When someone argues against abortion-on-demand or the legalization of marijuana, it’s an oft-repeated retort from libertarians and the Left: “Well, you can’t legislate morality.” Everyone nods solemnly, applauding the wisdom of the truism. Conversation stops.

But the truism couldn’t be more false. We can legislate based on morality. We do it all the time. To understand how, though, we must first give an account of what “morality” is.

A Sense of Morality Is Common to Humanity

In the past human beings believed that some things were right and other things were wrong. We didn’t know where this moral sense we all had came from or how we were able to make these judgments, but we knew it in our bones, as if by instinct.

There is undeniable evidence of an original common understanding of right and wrong across early cultures that were otherwise unconnected. The conclusions of these groups about the goodness or badness of certain actions were remarkably similar.

Different cultural groups explained this moral sense in different ways. Some thought it came from God, a common gift of general revelation to all mankind. Others thought our morals emerged from the natural order of the universe itself, a reflection of the “way things should be.” Still others believed reason was the source and clarifier of our moral sense.

Whatever the source, each group codified their common moral understandings into ordered, repeatable systems. These legal codes were either enforced by the governing authority, or remained well-known social traditions passed down as guiding lights. Regardless of their form, their authors knew exactly what they were making. Medieval theologian Thomas Aquinas’s famed definition of law reflects the sentiment of those days when it mandates that all law must be made “for the common good.”

From Common Understanding to Individual Feelings

But of course, we did away with all those ideas years ago. Traditional morals were something superstitious old people believed in, after all. And all things that seem superstitious and old are obviously false. (If you can’t hear the sarcasm here, you’re reading it wrong.)

The Enlightenment consensus expressed itself in a scrambling race toward greater individual freedom from constraints both real and imagined. Democracy became the ideal as our favorable views toward objective truth and morality waned. We wanted a system where everyone could follow his or her independent moral judgment, based on how the individual felt, and cast a vote accordingly. This system, we decided, would best determine what was best for everyone, and thus what should be made into law.

That is where we are. We still make moral judgments, but now we determine which moral judgments receive legal protection based on what the majority (or occasionally, a convincingly loud minority) approves. For example, most of us agree that speeding and stabbing people are both bad things to do, so we limit how often (if at all) everyone should do them.

Just Because We Disagree Doesn’t Mean There’s No Truth

So in a straightforwardly literal sense, arguing that “you can’t legislate morality” is false. Maybe those who use the phrase mean it in a different sense. Do they want to say that we can’t make public laws based on morality because trying to do so would be futile? After all, we sometimes disagree sharply about what’s morally right and wrong.

But disagreement doesn’t imply that there is no such thing as objective right and wrong, or rob us of any hope of moral consensus. We agree on the immorality of activities like murder or rape, so our disagreements over morality don’t imply that legislating based on morality is futile. Our cultural embrace of individually determined morality has just made it harder to reach agreement about what makes good law.

That insight, I think, leads us to the truth of the truism. “You can’t legislate morality” actually means “You shouldn’t make laws based on your morality, but on mine instead.”

Those who argue against legislating based on society’s current moral consensus, as expressed through its laws, are themselves making moral claims. The laws and the morality they’re based on are broken, they often say, because they restrain people from doing things that harm no one but themselves. Free expression is good, and harming others is bad. Laws that reflect these preferences are good laws.

Others argue that our current legal system is propped up by rotting pillars of social and economic inequality. Everyone should be made equal, and the laws should be used to root out unfairness, whether real or perceived, because equality is good and inequality is bad. These principled statements are laced with the language of morality.

We should keep discussing how much government ought to limit certain activities. But we should be honest with each other about our moral reasons for doing so. They’re nothing to be ashamed of; everyone has them. Until we all admit that we want our laws to aim at what’s good, we won’t be able to decide which good is best.

Connor Mighell is a third-year law student at The University of Alabama School of Law with an undergraduate degree in political philosophy from Baylor University. He is a staff writer at SBNation, and his work has been featured at The New Americana, Merion West, and The Dallas Morning News. He may be found on Twitter at @cmigbear.